Method of preparing photographic products



United States Patent METHOD OF PREPARING PHOTOGRAPHIC PRODUCTS William J. Knox, Jr., Edward F. Twardokus, andGordon D. Davis, Rochester, ,N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey NoDrawing. Application July 17, 1953, v Serial No. 368,816

3 Claims. (Cl. 117-34) This invention relates to an improved coating process and the product produced thereby. More particularly this invention concerns an improved process for coating photographic materials onto a base such as a film base or a paper base to produce an improved photographic product.

There are many instances in industry where it is desired to apply one or more relatively thin coatings or layers to various type bases. The photographic industry is a particular illustration of where relatively thin coatings are applied to various type bases including film and paper bases. In obtaining such coatings it is of course highly desirable in many instances that the coatings be relatively uniform and that the base thus coated be free of bare spots or other imperfections. it is also apparent that it is desirable to accomplish such coatings at good production speeds for etliciency of operation.

'It has already been suggested in .the art to utilize in coating compositions various surface-active agents for facilitating coating procedures or operations. Saponin has been used for this purpose. While this material is quite useful and has merit in a number of respects, it is a natural occurring material of vegetable origin. Therefore, the material may vary from batch to batch, both in quality and in composition. Hence, it is difficult to secure uniformity of results. Also, in some instances in photographic work certain batches of this agent may cause an increase in fog in the photographic materials, or a decrease of sensitivity or otherwise present various dimculties.

Accordingly, attention has been given to the finding of suitable synthetic surface-active agents which maybe used for purposes of the above type. Such synthetic agents, because ofthe controllable nature of their manufacture, usually would .be reproducible from batch :to batch both in chemical composition and behavior. While a number .of these synthetic agents have utility, it has been noted that they maybe deficient in certain'respects. For'exampie, while certain agents materially contribute to the ease of coating, they are not useful because of adverse photographic properties. Other of the coatingagents, while an improvementin some respects,.introduce problemsjin the application of a coating over an undriedcoating containing the agent. Various other difficulties and problems which have been encountered in this coating field'willbe referred to asthe descriptionproceeds.

-It is therefore apparent thatproviding agents of the class indicated which may be incorporatedin coatings,

ingoperations without theintroduction .ofderogatory. secondary etfects, is a highly desirable ,result. After e x tended investigation we have found that a certain group such as photographic coatings, and which facilitate coatof agents, which will he-idescribed in detail hereinafter,

maybe effectively used in coating operations.

"For a still furtherappreciation o'fsomeo'f the problems involved in jthefield under consideration, a brief reference Will'be made to amethod by which the coating maybe applied. This method which is a convenient means of 2,739,891 I Patented Mar. 27, 1956 app y ng the gelat n coating to the base o ves contact ing the base with the emulsion in a simple dip coating technique in which operation the material deposited ,on the base is in an amount greater than ordinarily desired in the finished coat. The base thus coated then passes thr h or in th n ty of some, rt f oa ng device which levels ofi or otherwise renders said coating more uniform and of the desired thickness. The run back of the excess coating composition will cause bubbles inthe coating vessel in the absence of a surface. active mate.- -rial such as is employedin accordance with our invention.

This invention has for one object t Provide an improved coating method. An important object is to provide a procedure particularly adapted for the coating of various proteinaceous coatings .on cellulosic bases. Another important object is to provide ,a method for coating photQ raPhic coatings such as .emulsions .upon base materials such as'paper or film base. :Still another object is .to provide an improved ,coatingaprocedure' whereby an undried first coating may be :followedby further coatings with good results. Still anotherobject is to provide a coat-ing procedure of the type aforementioned whereby there is smooth-rumback in relation to the leveling device. A still further object is to provide a process which .gives the overall result of relatively smooth and uniform coating on the base such as a paper base or other'cellulosic type base. Another object is to provide a new product comprising said base carrying a relatively uniform and regular coating, which while containing the surface-active {agent ,of the present invention, possesses unimpaired photographic properties. Other objects will appear hereinafter.

We have foundthatzthe compounds having the generic formula:

1-1 to 18 carbon latorns and R2 represents an aliphatic .radicalof -l to --,4 carbon atoms orphenyl or wcycloalkyl areerninently suited forenhancing the coating properties of .aqueousigelatin solutions whereby spotting and bubble formation is reduced v to a minimum or eliminated. Some of=the componnds in accordance .with the formula .given -whic -h;havebeen ;found;;t o be useful in coating operations ar Ql py :m thyl- :taurine, myristoyl methyl taurine, stearoyl methyl taurine,-palmitoyl methyl taun'ne, lauroyl methyl taurine, myristoyl butyl taurine, ricinoleyl methyl taurine and the like. These compounds are ordinarily employed in the form of the sodium salt although it is to be-understoodthat-other alkali metal or ammonium salts may be employed if desired. We ;have found that the addition of these materials to photographic emulsions or gelatin coating compositions generallypermitssmooth, even coatings and evenenables layers thereof such as the-emulsion in chilled or set condition but undried to be over-coated 'with another gelatin coating containing the-material referred to as a coating aid. This procedure -is referred to as a wet-on-weflcoating process.

The taurine compound in accordance with our invention is added to the liquid l-photographic emulsion or other aqueous gelatin solution in the proportion of 0.025- 2:2igramsand#preferably OTOZSto 1 gram per pound of the photographic emulsion orother gelatin solution --(of 2 ":10%.- concentration)'. This correspondstoa percentage of I0055-.5%':andpreferably BOSS-22% based -on the total weight -of the aqueous solution'of gelatin. Employmen-t of the coating aid in a -proportion outside of the -range=specified hasresulted in various cases "i-n;coatings Fhaving :defects arising from the ,fformation of bubbles ,in

the gelatin solutions.

rained.

Photographic emulsions are ordinarily eomprised of an aqueous solution of gelatin-containing a light sensitive material usually a silver salt such as silver chloride or silver bromide. The emulsion may contain'other added materials such as sensitizing dyes, hardeners, or other addenda. Descriptions of photographic emulsions are found in the prior art such as in the publication Fundamentals of Photographic Theory by James and Higgins, published in 1948 by John Wiley & Sons, Chapter 2. Therefore any further detailed description here appears to be unnecessary. I i

The base to be coated may be composed of any of the usual conventional film base materials. This may be a sheeting of a cellulose ester such as cellulose nitrate or an organic acid ester of cellulose such as cellulose acetate, cellulose acetate propionatc or cellulose acetate butyrate. It is often desirable to first apply a subbing layer to the cellulose ester base to contribute to the adhesiveness of the photographic emulsion thereto as is well known in the art. before the application of the emulsion is'usually coated with a coating of barium sulfate in suspension in a colloid such as gelatin. A description of photographic paper is found in Kodak data book th edition Kodak Papers pages 3 and 4. A base material of this type would preferably be employed for preparing photographic paper in accordance with the present invention.

The coating procedure utilized may comprise any of the standard procedures employed in the industry. As an instance of such procedure, the paper base to be coated is passed through a trough or other reservoir whereby a coating is applied to the paper base. Ordinarily the coat ing is applied in greater thickness than desired on the finished product. In order to reduce the thickness and smooth the surface some means such as an air brush is directed angularly against the coating causing runback of the coating composition and resulting in an even surface. Instead of the air brush some other means of smoothing the coating and reducing its thickness such as a doctor blade or the like may be employed.

We have found that by incorporating an acylated taurine derivative in a proteinaceous coating composition the coating of that composition on a support therefor is facilitated and a high quality uniform coating is obln incorporating a coating aid, as described herein, into an aqueous gelatin solution, it is usually desirable to add it in the form of a dilute aqueous solution such as of 2% concentration. In'this manner uniform distribution thereof in the proteinaceous coating composition is obtained. The following examples illustrate our invention:

Example I A fine-grain positive speed silver bromoiodide emulsion was prepared containing 6.5 gelatin and weighing 12 lbs. per mol of silver halide. To the emulsion composition was added in the form of its 2% solution 0.89 gram of the sodium salt of myristoyl methyl taurine for every mol of silver halide present therein. The emulsion was coated out onto a standard cellulose acetate photographic film support. The coating was found to be very uniform and free of repellency spots, mottle and streakiness.

Example 2 A negative speed, panchromatically sensitized silver As for paper base this material 7 bromoiodide photographic emulsion was prepared and contained 6.5% of gelatin and weighed 8.9 lbs. per mol of silver halide. To the emulsion composition was added in the form of its 2% solution 0.22 gramof thesodium salt of myristoyl methyl taurine for every. mol of silver halide present therein. This emulsion was coated out onto a film support at a coverage of 210 sq. ft.,per mol of silver halide. A uniform coating was obtained and the coating was substantially free of repellency spots.

p was added per liter of the gelatin solution.

Examples t A 1.7% solution of gelatin in water was prepared and added thereto was 0.11 gram of the sodium salt of myristoyl methyl taurine per liter of solution. This solution coated out satisfactorily at a coverage of 6,600 sq. ft. per liter of solution on a chilled, wet emulsion layer which emulsion layer also contained the sodium salt of myristoyl methyl taurine.

Example 4 Example 5 A solution of gelatin of 8.6% concentration in water was prepared containing magenta dye. There was added thereto in the form of its 2% solution 0.19 gram of the sodium salt of lauroyl methyl taurine per liter of solution. The solution was coated out onto a cellulose acetate support and coated uniformly and satisfactorily at a coverage of 530 sq. ft. per liter of solution.

Example 6 An 8.6% aqueous gelatin solution was prepared containing magenta dye. 0.19 gram of the sodium. saltof stearoyl methyl taurine was added per liter of gelatin solution. The solution was coated out onto a cellulose acetate support and was found to coat uniformly and without defects, the coating having been applied at a coverage of 530 sq. ft. per liter of solution.

Example 7 An aqueous gelatin solution of 8.6% concentration was prepared, which solution contained a magenta dye. 0.19 gram of the sodium salt of myristoyl butyl .tau rine The solution was coated out onto a cellulose a'cetate support at a coverage of 530 sq. ft. per liter of solution. The'solution was found to coat uniformly and gave a coating free of defects.

Emulsion coatings such as are applied in accordance with our invention may be tested for repellency spots, or coating defects by exposing the coating to a carbon are light which light prints out the emulsion thus darkening'the coated area and emphasizing the bare repellency' spots. The number of spots counted in a given area as compared with the spots obtained when treating standard coatings in this manner gives an indication of the repel,- lency value of the coating being tested. Ordinarily in coatings in accordance with our invention in an area of 10 sq. ft. it is only occasionally that any repellency spots are observed and then only on the order of one, whereas withotherwise identical coatings in which a coating aid is not employed numerous spots appear. Also in the case of gelatin compositions in accordance with our invention foaming or bubbling is substantially eliminated in contrast with similar compositions in which, surface active agents are not added.

The following examples illustrate the preparation of photographicpaper employing coatingcornpositions in accordance with our invention.

Example 8 ,A gelatinous silver halide emulsion was prepared containing 7.6% of gelatin and 1.6% of silver salts. There was then added to the emulsion 0.15 gram of the sodium salt of oleoyl methyl taurine per lb. of .thefsilver halide emulsion, the salt being added in the'f orin of its 2% soldtion. The thus formed emulsion was coated out onto a baryta coated paper base and the coating so formed was set by chilling (such as 50). Without drying the coating the same was overcoated with an aqueous solution of gelatin containing 2.5% gelatin and 0.13 gram of the sodium salt of oleoyl methyl taurine per lb. of coating solution. Both coatings were then chilled and dried. It was found that the overcoating effectively adhered to the emulsion coating over which it was applied and that the resulting product was free of defects and spots.

Example 9 A gelatinous silver halide emulsion was prepared containing 7.1% of gelatin and 2% of silver salts. To every lb. of emulsion was added 0.24 grams of the sodium salt of oleoyl methyl taurine in the form of its aqueous 2% solution. The emulsion was coated onto a baryta coated paper base and the coating was set by chilling the same. An overcoat of an aqueous solution of gelatin containing 2.5 of gelatin and 0.73 gram of saponin per lb. of solution was applied over the emulsion layer which was still in a wet condition. Both coatings were then chilled and dried. A product was obtained in which the overcoating adhered uniformly to the emulsion layer.

Example 10 A gelatinous silver halide emulsion was prepared containing 8.6% gelatin and 2.9% silver salts. To every lb. of the emulsion was added 0.3 gram of the sodium salt of oleoyl methyl taurine in the form of its 2% aqueous solution. The emulsion thus obtained was coated onto a baryta coated paper base and the emulsion coating thus obtained was set by chilling. There was then applied over the emulsion while still in an undried condition an overcoating of 2.5% gelatin solution containing 0.13 gram of oleoyl methyl sodium taurine per lb. of solution. Both coatings were chilled and dried. The overcoating was found to adhere uniformly to the emulsion coating to which it had been applied.

Example 11 A gelatinous silver halide emulsion was prepared containing 7.3% gelatin and 3.6% of silver salts. To every lb. of emulsion was added 0.5 gram of the sodium salt of oleoyl methyl taurine in the form of a 2% solution. The emulsion so formed was coated onto a baryta coated paper base, was set by chilling and the emulsion was dried. The resulting product was free of defects and had good uniformity.

Example 12 A gelatinous silver halide emulsion was prepared containing 6.9% of gelatin and 2% of silver salts. To every lb. of the emulsion was added in the form of its 2% solution 0.46 gram of the sodium salt of oleoyl methyl taurine. The resulting emulsion was coated onto baryta coated paper base and was set by chilling but not dried. There was then applied thereto an overcoating of 2.5% gelatin solution containing 0.2 gram of the sodium salt of oleoyl methyl taurine per 1b. of solution. Both coatings were then chilled and dried. A product was obtained free of defects and having good uniformity.

Example 13 A gelatinous silver halide emulsion was prepared containing 5.4% of gelatin and 3.9% of silver salts. To every lb. of the emulsion was added 0.55 gram of the sodium salt of oleoyl methyl taurine in the form of its 2% solution. The emulsion was coated out onto paper base, was set by chilling and the emulsion layer was then dried. A

photographic paper was prepared free of defects and hav ing good uniformity.

Example 14 Concentration of Rieinoleoyl Amount of Methyl Taurine Repellency Sodium Salt, Spots Per Grams Per Lb. l0 Sq. Ft.

of Emulsion Experiment Number one Myriad 0. 14 7 The photographic properties of the paper obtained in each one of the instances here were acceptable.

We claim:

1. A method of preparing a coated product which comprises applying to a support a gelatin silver halide photographic emulsion containing as the sole surface active material therein .0055.5% of a taurine having the structural formula:

Where M is an alkali metal substituent, R1 represents an aliphatic hydrocarbon radical of 11-18 carbon atoms and Rz represents a substituent selected from the group consisting of the alkyl radicals of 14 carbon atoms, phenyl and cyclo alkyl, setting the coating so applied, then applying thereto, while still wet, a layer of an aqueous gelatin composition containing as the sole surface active material .0055.5% of the same taurine compound as employed in the photographic emulsion layer, followed by drying the product thus obtained.

2. A method of preparing a coated product which comprises applying to a support a gelatin silver halide photographic emulsion containing as the sole surface active material .005 5.5 of an alkali metal salt of oleoyl methyl taurine, setting the coating so applied, then applying thereto, while still wet, a layer of an aqueous gelatin composition containing as the sole surface active material .0055.5% of an alkali metal salt of oleoyl methyl taurine, followed by drying the product thus obtained.

3. A method of preparing a photographic film which comprises applying to a film base a gelatin silver halide photographic emulsion containing as the sole surface active material therein .0055.5% of the sodium salt of oleoyl methyl taurine, setting the coating so applied, then applying thereto, while still wet, a layer of an aqueous gelatin composition containing as the sole surface active material .0055.5% of the sodium salt of oleoyl methyl taurine followed by drying the product thus obtained.

References Cited in the file of this patent UNITED STATES PATENTS 1,932,180 Gucnther Oct. 24, 1933 2,146,873 Wilmanns Feb. 14, 1939 2,269,169 Van Dehoef Jan. 6, 1942 2,368,287 Chilton Jan. 30, 1945 2,651,645 Cross Sept. 3, 1953 

1. A METHOD OF PREPARING A COATED PRODUCT WHICH COMPRISES APPLYING TO A SUPPORT A GELATIN SILVER HALIDE PHOTOGRAPHIC EMULSION CONTAINING AS THE SOLE SURFACE ACTIVE MATERIAL THEREIN .0055-.5% OF A TAURINE HAVING THE STRUCTURAL FORMULA: 